BUILDING SCIENCE SERIES 42

Design Loads for

Inserts

Embedded in Concrete
The Building Science Series

The Building Science Series disseminates technical information developed at the National Bureau of Standards on

building materials, components, systems and whole structures. The Series presents research results, test methods and

performance criteria related to the structural and environmental functions and the durability and safetj^ characteristics

of building elements and systems.

These publications, similar in style and content to the NBS Building Materials and Structures Reports (1938-59)

,

are directed toward the manufacturing, design, construction and research segments of the building industry, standards

organizations and officials responsible for building codes. The material for this Series originates principally in the Building Research Division of the NBS Institute for Applied Technology. The publications are divided into three general groups: Building Sj^stems and Processes; Health,

Safety, and Comfort; and Structures and Materials. Listed below are other publications in the category of

Structures and Materials

• Interrelations Between Cement and Concrete Properties: Part 1, Materials and Techniques and Trace Elements

(C13 29/2:2) 35 cents

• Weather Resistance of Porcelain Enamels: Effect of Exposure Site and Other Variables After Seven Years

(C13.29/2:4) 20 cents

• Interrelations Between Cement and Concrete Properties: Part 2, Sulfate Expansion, Heat of Hydration, and Autoclave Expansion (Cl3.29/2:5) 35 cents

• Some Properties of the Calcium Aluminoferrite Hydrates (C13.29/2:6) 20 cents

• Organic Coatings, Properties, Selection, and Use (013.29/2:7) $2.50

• Interrelations Between Cement and Concrete Properties: Part 3, Compressive Strengths of Portland Cement Test Mortars and Steam-Cured Mortars (Cl3.29/2:8) 35 cents

. Thermal Shock Resistance for Built-Up Membranes (013.29/2:9) 20 cents

• Shrinkage and Creep in Prestressed Concrete (013.29/2:13) 15 cents

• Experimental Determination of Eccentricity of Floor Loads Applied to a Bearing Wall (013.29/2:14) 15 cents

• Interrelations Between Cement and Concrete Properties: Part 4, Shrinkage of Hardened Portland Cement Pastes (013.29/2:15) 75 cents

• Causes of Variation in Chemical Analyses and Physical Tests of Portland Cement (013.29/2:17) 40 cents

. A Study of the Variables Involved in the Saturating of Roofing Felts (013.29/2:19) 30 cents

• Proceedings of a Seminar on the Durability of Insulating Glass (013.29/2:20) 75 cents

• Hail Resistance of Roofing Products (013.29/2:23) 25 cents

• Natural Weathering of Mineral Stabihzed Asphalt Coatings on Organic Felt (013.29/2:24) 30 cents

. Structural Performance Test of a Building System (013.29/2:25) $1.25

• 1964 Exposure Test of Porcelain Enamels on Aluminum—Three Year Inspection (013.29/2:29) 25 cents

• Flexural Behavior of Prestressed Concrete Composite Tee-Beams (013.29/2:31) 25 cents

• Compressive Strength of Slender Concrete Masonry Walls (013.29/2:33) 40 cents

• Strength of Masonry Walls under Compressive and Transverse Loads (013.29/2:34) 70 cents

• Interrelation Between Cement and Concrete Properties: Part 5, Freezing and Thawing Durability, Saturation, Water Loss and Absorption, Dynamic Modulus (013.29/2:35) $1.25

• Interrelations Between Cement and Concrete Properties: Part 6, Compilation of Data from Laboratory Studies (013.29/2:36) $1.25

• 1939 Exposure Test of Porcelain Enamels on Steel, 30-Year Inspection. (013.29/2:38) 25 cents

• Engineering Aspects of the 1971 San Fernando Earthquake. (013.29/2:40) $3.00

Send order (use Superintendent of Documents Catalog Nos.) with remittance to: Superintendent of Documents, U.S. Government Printing Office, Washington, D.O. 20402. Remittances from foreign countries should include an additional one-fourth of the purchase price for postage.

[See maihng list announcement on last page.]
UNITED STATES DEPARTMENT OF COMMERCE • Peter G. Peterson, Secretary

Design Loads for Inserts Embedded in Concrete

T. W. Reichard, E. F. Carpenter, and E. V. Leyendecker

Building Research Division

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

JBuilding Science Series 42

Nat. Bur. Stand. (U.S.), BIdg. Sci. Ser. 42, 28 pages (May 1972)

CODEN: BSSNBV

Issued May 1972

For sale by the Superintendent of Documents, U.S. Government Printing Ofl&ce Washington, D.C. 20402 (Order by SD CataJog No. C 13.29/2:42), Price 35 cents

Stock Number 0303-0965
Library of Congress Catalog Card Number: 75-189154
Contents

Page Notation v Conversion Units v

1. Introduction j

1.1. General 1

1.2. Objective 1

2. Materials and Test Specimens 1

2.1. Inserts • 1 2.1.1. Type 1 Insert 2

2.1.2. Type 2 Insert 2

2.1.3. Type 3 Insert 2

2.2. Concrete 3

2.2.1. Normal Weight Aggregate Concrete 3

2.2.2. Lightweight Aggregate Concrete 3

2.3. Reinforcement 3

2.4. Test Specimens 4

2.4.1. 4X4 Specimens 4

2.4.2. 4 X 22 Specimens 5

2.4.3. 4 X 16 Specimens 5

2.4.4. Waffle Slab Specimen 6

3. Test Equipment and Procedures 6

3.1. Static Tests 6

3.1.1. Static Test Equipment 6

3.1.2. 4X4 Specimen Test Procedure 6

3.1.3. Continuous Span 4 X 22 Specimen Test Procedure 6

3.1.4. Simple Span 4 X 22 Specimen Test Procedure 7

3.1.5. Waffle Slab Specimen Test Procedure 7

3.2. Sustained Load Tests 7

3.2.1. Sustained Load Test Equipment 7

3.2.2. Sustained Load Test Procedure 7

3.3. Fatigue Loading Tests 7

3.3.1. General 7

3.3.2. Fatigue Loading Test Equipment 7

3.3.3. Fatigue Tests on 4 X 4 Specimens 8

3.3.4. Fatigue Tests on 4 X 16 Specimens 8

4. Discussion of Results 8

4.1. General 8

4.2. Effect of Aggregate and Insert Type 8

4.3. Concrete Strength-Weight Effects 9

4.4. Effect of Flexural Cracking 12

4.5. Effect of Reinforcement Cover and Spacing 15

4.5.1. Concrete Cover 15

4.5.2. Reinforcement Spacing 15

4.5.3. Waffle Slab Ribs 15

4.6. Sustained Load Behavior 17

4.7. Fatigue Load Behavior 18

4.7.1. General 18

4.7.2. Normal Weight Concrete 18

4.7.3. Semi-Lightweight Concrete 18

4.7.4. Variation of Insert Type and Ratio, R 19

4.7.5. Fatigue Failures in Connecting Hardware 19

4.8. Angular Load Effect 20

III
Page

o. Summary and Conclusions 20

5.1. General 20

5.-2. Aggregate and Insert Type 20

5.3. Concrete Strength 20

5.4. Concrete Flexural Cracking 20

5.5. Reinforcement Quantity and Cover 21

5.6. Sustained Load 21

5.7. Fatigue Load 21

5.8. Angular Load Effect 21

5.9. Experimental Scatter Factor 21

6. Design Criteria 21

6.1. Design Recommendations 21

6.1.1. Design Safety Margin 21

6.1.2. Design Equations 21

6.2. Precautions and Limitations 22

6.2.1. Connecting Hardware 22

6.2.2. Insert Spacing 22

6.2.3. Inserts Other than Those Tested 22

6.2.4. Inserts in Lightweight Aggregate Concretes 22

6.2.5. Installation of Inserts 22

7. References 23

IV
Notation

// = compressive strength of concrete in psi

kip = 1,000 lb P = pull-out load of an insert in kips

Pi = pull-out load of an insert in a 4 X 4 specimen* in kips

Pih = calculated pull-out load in a normal weight

concrete 4X4 specimen = 1.63 + 0.18\///

in kips

Pis = calculated pull-out load in a semi-lightweight

concrete 4X4 specimen = 3.06 -j- 0.13\//c' in kips

Piu = calculated pull-out load in a 4 X 4 specimen = 2.0 + 0.0012TF,V/c' in kips

Pn — normalized pull-out load for a reference

strength concrete _ p Vreference jc Yv^&

Vactual/c'

Pmax = maximum load applied to an insert in a

fatigue test in kips

Pmin = minimum load applied to an insert in a

fatigue test in kips

R = ratio of cycHc loading = Pmin/Pmax

Wc = unit weight of concrete in lb/ff

Wh = unit weight of normal weight concrete in

Ib/ft^

Wi = unit weight of lightweight concrete in Ib/ft^ Ws = unit weight of semi-lightweight concrete in

Ib/ft^

Insert Pull-Out Load Reduction Factors AppUed to the General Pull-Out Load Formula,

Piu = 2.0 + O.OOUWcVfc'

<f> = total reduction factor

(l>cf = minimum combined fatigue reduction factor

<Ac//i = combined fatigue reduction factor for normal

weight concrete = <l>eh<i>/iL

<t>cfs = combined fatigue reduction factor for semilightweight concrete = <{>es(t>fs

(l)eh = experimental scatter reduction factor for inserts embedded in normal weight concrete

<t>es = experimental scatter reduction factor for inserts embedded in semi-lightweight concrete

(t>/ii, = fatigue load reduction factor for inserts embedded in normal weight concrete

0/s = fatigue load reduction factor for inserts embedded in semi-lightweight concrete

<^)s = sustained load reduction factor

<t>i = flexural cracking reduction factor for inserts embedded in slabs spanning more than four

feet.

Conversion Units

Length

1 in = 0.0254 meter

1 ft = 0.3048 meter

Area

1 in2 = 6.4516 X 10-" meter^

1 W = 0.09290 meter^

Force

1 lb (Ibf) = 4.448 newton

1 kip = 4448 newton

Pressure, Stress

^.1 psi = 6895 newton/meter^

1 psf = 47.88 newton/meter^

Mass/Volume

1 Ih/W {\hm/W) = 16.02 kilogram/meter'

Cement Measure

1 sack is approximately 94 lb = 42.6 kilogram

Reinforcement Steel No. 3 bars—Nominal diameter = f in = 0.0095

meter

No. 4 bars—Nominal diameter = ^ in = 0.0127

meter

No. 5 bars—Nominal diameter = | in = 0.0159

meter

* Nominal width and length of specimen in feet. V

Design Loads for Inserts Embedded in Concrete

T. W. Reichard, E. F. Carpenter, ^ and E. V. Leyendecker

Detailed test procedures are presented for a research program on cast-in-place inserts embedded in reinforced concrete. Three types of inserts, two of malleable iron and one of ductile steel, capable of receiving a f-inch threaded rod were tested. Other variables included concrete aggre- gate type, concrete strength, reinforcement cover and spacing, angular loading, flexural cracking, sustained load, and fatigue loading.

It was found that the pull-out load for an insert could be approximated by a linear function of the concrete unit weight and square root of the compressive strength in a statically loaded reinforced concrete slab. The effect of other variables is related to the in.sert pull-out loads in these slabs. Design recommendations are presented.

Key words: Anchors; concrete slabs; design loads; fatigue; inserts; pull-out loads; sustained load.

1. Introduction

1.1. General

As the cost of construction continues to increase, more and more designers are looking for methods to optimize floor space utiUzation. One method com- monly used is to suspend from the ceiling equipment

which might otherwise be occupying premium floor space. An increasing number of devices suitable for suspending such loads are being used in industrial,

institutional, and commercial buildings.

One such device being used with concrete slab

construction is an anchor commonly called a concrete insert. These concrete inserts are made to

receive either an ordinary threaded rod, a bolt head,

or a special nut. They are simply fastened to the

formwork prior to placing the concrete. This simplicity offers advantages over other devices such as embedded anchor bolts which must penetrate the

normally reusable formwork. Ordinarily, the manufacturer's catalogs are the only source of data

regarding the load-carrying capacity of most of these

inserts. Table 1 is a listing of such catalog data for some typical inserts made to receive f-in diameter

threaded rods or bolts. A recent pubhcation [1]^ presents some load

capacity data for two types of inserts. These data

indicate that the load capacity of inserts is partially a function of their embedded length. In an investigation of drilled-in anchors, Adams [2] presents data

which also indicate that the embedded length of the

insert is a major variable. Adams also shows that the

load-carrying capacity of his anchors was a function

of the concrete strength. Kennedy and Crawley [3], in a report of an investigation concerning the load

capacity of form anchors for mass concrete, observed

that the failure of the concrete around the anchors

'Present address: The Mitre Corporation, 1820 Dolley Madison Blvd., McLean, Va. 22101.

^ Figures in brackets indicate the literature references at the end of

this paper.

was influenced by the bending moments. As far as is known, no systematic study of the factors which

affect the load carrying capacity of inserts in rein- forced concrete slabs has been published. It is known

that some manufacturers have investigated certain

variables although the scope and test results are not known.

1.2. Objective

Due to the limited availability of concrete insert data the Building Research Division, in cooperation

with the Post Office Department, conducted a comprehensive study of the variables influencing

the ultimate load carrying capacity of some com- monly used inserts. The objective of the investigation was to propose design criteria for inserts embedded in reinforced concrete slabs such as those found in postal facilities. The following variables were studied:

a. Insert type

b. Concrete aggregate type

c. Concrete strength

d. Reinforcement cover

e. Reinforcement spacing

f. Angular load effect

1. Angular displacement of insert

2. Angular insert load

g. Flexural cracking effect

h. Sustained load

i. Fatigue load

2. Materials and Test Specimens

2.1. Inserts

Three different inserts were used in the main part

of the investigation. In preliminary tests [4], six different insert types were used, but the number was

reduced to three for this study to satisf>- a Post

1
Table 1. Typical manufacturer''s catalog data for \-inch inserts

Insert Catalog name Type of metal Overall length

Manufacturer's

ultimate

strength in concrete

Manufacturer's working

load

A Universal-all size nut .... Concrete insert Malleable iron in

3IH

2i3f

3i3^

3f

3

1 ^

lb lb 3,000

B Zinc casting alloy . . . . do12,500

6,900

7,650

10,000

12,500

15,300

11,900

12,400

C do 3,000

D 3,020

E

Malleable adjustable

Threaded insert Malleable ironSteel F do Gray cast iron 3,100

3,800

3,020

3,020

G do Malleable iron H Rocket do

I Kohler Gray cast iron

T Steel K Mitey-Mite Malleable iron 6,600 2,500

Note: Inserts recommended as suitable for use with 4^ in thick concrete slabs.

Office Department specification requiring malleable

iron inserts suitable for attaching f-in-diameter

threaded rods. The deleted inserts were made from

gray cast iron, would not receive a |-in-diameter

threaded rod, or were special purpose inserts [4].

The specification requiring malleable iron inserts was probably designed to guard against the use of a

brittle material such as gray cast iron. A ductile

steel insert does not meet the strict wording of the

specification although one was included in this investigation.

2.1.1. Type 1 Insert The Type 1 insert used in this investigation is described in the catalogs as a malleable iron threaded

insert, especially designed for use where impact or vibration is a factor. Figure 1 is a photograph of this

insert, and it indicates the significant dimensions.

These inserts were fastened to the plywood concrete form with 1-in roofing nails driven through the two

side lugs visible at the bottom of the insert in

figure 1.

2.1.2. Type 2 Insert The Type 2 insert illustrated in figure 2, is called a threaded insert by the manufacturer. The closed

end spool is machined from mild steel. The loop

welded to the spool is 0.26-in-diameter steel wire,

with an ultimate strength of about 65,000 psi.

These inserts are set in the concrete form by using a

plastic plug or cup which is nailed to the form prior to forcing the insert spool over the cup.

2.1.3. Type 3 Insert The Type 3 malleable iron insert illustrated in

figure 3 is also called a threaded insert by the manuFiGURE 1. Type 1 insert. Figure 2. Type 2 insert.

2
Figure 3. Type 3 insert.

facturer. These inserts were set by driving 1-in roofing nails into the form through the two side lugs

visible at the bottom of the insert in figure 3.

2.2. Concrete

Table 2 describes the seven types of aggregates

used in making the concrete. As indicated in this

table, two of the coarge aggregates were normal

weight and five were expanded-shale lightweight

aggregates. All concretes were mixed in 6 to 10 cu yd

commercial transit mixers in 3 cu yd batches or

larger. The normal weight concretes were standard

mixes for the supplier, as were the concretes made

with the L-1 lightweight aggregates. For the concretes made with L-2, Ij-3, L-4, and L-5 lightweight

aggregates, the readymix contractor supplied the

cement and usually the sand. The lightweight aggre- gate was measured and placed in the mixer by NBS

personnel. These concretes were proportioned as recommended by the aggregate producer, except

that water was added until a suitable coasistoncy

^vas attained. A 4 to 6 in slump was the target consistency for the normal weight concrete, and a 2 to 4 in slump for the lightweight aggregate concrf^te. Some problems were encountered in accjuiring the

desired unit weight and consistency with tlie rcjadymix L-1 semi-lightweight concrete. These; difficultie.s ^vere probably a result of tht; ratlK;r small batch

sizes in the large mixers. Control cylinders (G-inX

12-in) were cast from each batch of concrete for determining compressive and splitting tensile strengths. All test specimens were consolidated in the

mold by internal vibration. After removal from the

molds, all specimens were air-dried until tested. The specimens were tested at various ages, ranging

from 5 to 42 days. Compressive strength determinations were made in accordance with ASTM Method

C-39. The splitting tensile strength tests were made

in accordance with ASTM C-496, except for the

curing conditions.

2.2.1. Normal Weight Aggregate Concrete

Table 3 gives the properties of the concrete mixes

made with normal weight aggregates. The sand to stone ratio was 45 to 55 for all mixes except H-2

and H-2a. For these two mixes the proportions were

40 to 60.

2.2.2. Lightweight Aggregate Concrete

Table 4 is a listing of the concretes made with the

lightweight aggregates. These concretes were all semi-lightweight^ except for L-4. The proportions

recommended by the producer of the lightweight

aggregate were used throughout this investigation.

2.3. Reinforcement

All principal reinforcement was No. 5 deformed,

intermediate grade steel bars placed on bolsters to provide the required concrete cover. Temperature

steel was generally No. 3 bars spaced at about 12 in on centers.

' Semi-lightweight concrete is a concrete containing the coarse lightweight

aggregate, but with a natural sand replacing the lightweight aggregate fines.

Table 2. Aggregate descriptions

Aggregate

designation

H-1

H-2

L-1.

L-2.

L-3.

L-4.

L-5.

Max.

size

Type of aggregate

Coarse

Crushed stone

.

Gravel Expanded shale Expanded shale Expanded shale Expanded shale Expanded shale

Fines

Natural sand . . Natural sand . . Natural sand . . Natural sand . . Natural sand . . Expanded shale Natural sand . .

Source of aggregate

Coarse

Md.

Md.

Va. Ga.

111. Calif. Texas

Note: Although these lightweight aggregates are identified as being expanded shales, the actual raw materials could be either

shale, clay, or slate.

3
Table 3. Concrete mixes made with normal weight aggregates

Concrete Nominal

cement

content

Measured

slump

Age at

test Splitting

strength

Compressive

strength

sacks /yd^ in days psi psi

H-1 Kt.) 7 H-2 5 4 7 380 3150 H-IA 6 5 27 3950 H-2A 6 5 19 450 4110

S-1 5 6 21 3830

S-2 5 6i 15 3940

S-3 o (J 01 iU S-4 4 7 18 2640 W-1 5 5 7 420 3330

F-1 5 2| 10 510 5280

F-3 5 13 340 3830 r-4 0

Q CAn ooUU

C-1 5 5§ 34 3630 C-3 5 5 40 440 5010 X-IA 5 4i 23 460 4560 X-IB oDS X-2A 5 4i 24 445 4560 X-2B 5 4i^2 28 338 3670 X-3A 41 6 7 340 3180 X-3B 7 3 and 6 14 434 5570 X-4A 4i 6 20 334 3440 X-20A 5 5 10 320 4090 X-20B 0 6 9 320 3100 X-20C 5 4 7 312 3200

Note: All normal weight concretes were made with the H-1 crushed stone coai-se aggregate except for concretes H-2 and H-2A

which were made with the H-2 gravel.

2.4. Test Specimens

Four general types of concrete test specimens were used for the inserts in this investigation. Except

for one waffle slab all specimens were 4| in thick and

were designed as one-way slabs. The slab length and

width were dictated by the purpose for which it was made as discussed below. All 4|-in thick specimens

were cast in wood forms, with the inserts nailed to the bottom of the form. The specimens were turned

over for testing convenience.

2.4.1. 4X4 Specimens

Ninety percent of the almost 400 specimens

tested were nominal 4X4 specimens. The actual

Table 4. Concrete mixes made with lightweight aggregates

Concrete

L-1 . .

,

L-2...

L-3.., L-4.

.

L-5.. L-1 A.

L-2A.

C-2. . C-4..

F-2.. X-2C

X-2D

Aggregate

L-1 L-2

L-3 L-4

L-5

L-1 L-2

L-1

L-1 L-1

L-1

L-1

Nominal

cement

content

sacks Iyd^ 6H

H

5i

Measured

slump

In ^

1H

2

^23

28^

3i

4

3

Fresh

unit weight

Ih/ft^ 117 114

11596

120

119

117

119

118

120

121 119

Age at

test

days

' 35

8

17

58

1920

3142

1131

Splitting

strength

psi270

350 400

280

330

370 480

' 230

440

360

Note: All concretes were" semi-lightweight (sanded) except for L-4 which was lightweight.

4
dimensions were 42 in X 45 in X 4| in thick. This

specimen size was arrived at after preliminary

tests [4] indicated that a smaller specimen would

not be satisfactory for single insert pull-out tests. A

single insert was cast in the specimen, with the rein- forcement placed symmetrically about the insert,

and with the principal steel placed parallel to the

long dimension, with f-in cover. Figure 4 is a photograph of a static pull-out test on

a 4 X 4 specimen and illustrates a typical failure of the concrete. It is obvious from this illustration that

the failure zone would be changed if the test stand

supports were closer together.

2.4.2. 4 X 22 Specimens

Seven 4 X 22 specimens were cast with a width of 42 in and a length of 22 ft. The principal reinforcement in all these slabs was No. 5 bars at 6 in on

centers and with |-in cover. Four of the seven speci- mens were designed as one-way slabs to be con- tinuous over three supports with two 10-ft spans. Negative moment reinforcement for these slabs was

No. 5 bars at 8 in on center, placed with f-in cover from the top surface as cast. Nineteen inserts were

cast in each continuous slab at about 12 in on

center. These slabs were cast from concrete designated as S-1, S-2, S-3, and S-4. In addition to the

long slabs, four companion 4X4 slabs with single

inserts were cast with the S-1, S-2, and S-3 concretes. Figure 5 illustrates a 4 X 22 continuous slab

ready for a test to determine the effect of bending

moment on the pull-out strength of the insert. The

positions of the 19 inserts were indicated by the eyebolts. It should be noted that, although the speci- mens were cast in the orientation they would be on

the job, all slabs were turned over for testing convenience.

Three additional 4 X 22 specimens, designed as simple span, one-way slabs, were tested with a 20-ft span to investigate the pull-out strength of inserts in long thin slabs. Five inserts were cast in each of these specimens. One insert was at midspan, two

were at 30 in on either side of midspan, and two were

Figure 4. Static test on 4 specimen.

Figure 5. Sialic test on 4 22 specimen.

at 31 in from either end. The two inserts near the

ends were tested as if they had been cast as separate

4X4 control specimens. These three specimens were

cast from concrete designated as X-20A, X-20B,

and X-20C.

2.4.3. 4 X 16 Specimens

Four 4 X.16 fatigue test specimens, with a width

of 45 in and a length of 15 ft 9 in, were cast from

each of the X-2A, X-2B, X-2C, and X-2D concretes. The inserts were spaced so that each specimen had

two inserts, spaced at 64 in from either end, available

for fatigue tests on a 10-ft span. In addition, most

specimens contained inserts placed at 24 in from

either end, for simulated 4X4 pull-out tests. Figure

6 is a photograph of a 4 X 16 specimen prior to

Figure 6. Fabrication of ^ Y. 16 specimens.

placement of the concrete. The two top bars visible in this picture were for prevention of damage while

handling. These specimens were made in order to determine the effect of bending moment on the

pull-out strength of inserts subject to cyclic fatigue

loading.

5
2.4.4. Waffle Slab Specimen

A single waffle slab specimen with overall dimensions of 6 ft X 15 ft X 12 in was cast from the

normal weight concrete designated as W-1, using

10-in deep 30-in X 30-in metal pans. Figure 7 is a photograph of the waffle slab prior to placement of the concrete. Two No. 5 bars were placed f in from

the bottom of each 6-in rib in the long direction, and

two No. 5 bars were placed on top of these in the

opposite direction. Welded wire fabric (6X6-

10 X 10) was placed over the pans. Inserts were

placed at each of the interior intersections (36 in on

centers) of the ribs.

Fkujue 7. Fabrication of wajlic slab spcciinrn.

3. Test Equipment and Procedures

3.1. Static Tests

.3.1.1. Static Test Equipment

Figures 4, 5, and 8 illustrate the equipment used

for applying short term static pull-out loads to the

inserts embedded in the concrete specimens. The

apparatus in figure 4 was used for the 4X4 speci- mens, while that in figures 5 and 8 was used for the

4 X 22 specimens. The basic parts were:

a. a steel stand with supports spaced at the re- quired distance;

b. a center-hole 60-kip hydraulic ram powered

with a remote hand-operated pump;

c. a center-hole 60-kip load cell; d. an X-Y plotter for recording the output of the

load cell; and

e. a f in high-strength steel pull-rod.

Figure 8. Close-up of static test on 4 X 22 specimen.

When testing the 4X4 specimens, the test stand

had an effective span of 42 in. The effective span of the stand for the longer specimens was the same as the span of the test specimen. The test stand was

always placed so that its span was in the same direction as the main reinforcement.

For some tests, the vertical movement of the

insert was measured by using an LVDT displacement transducer. The LVDT, visible in figure 8, was mounted on the pull-rod and the core rested on a

bridge, supported at the mid-span edges of the slab. The output of the LVDT was fed to the X-axis

of the X-Y plotter used with the load cell so that a continuous plot of the load versus vertical movement

was recorded.

3.1.2. 4X4 Specimen Test Procedure

The testing procedure was rather simple for the

short-term static tests. The tensile pull-out load was applied to the insert at a uniform rate, until

failure occurred. The maximum load attained during

the tests was called the pull-out load of the insert in a 4X4 specimen (P4) . During preliminary tests [43,

there were indications that the maximum load was a

function of the rate of loading. For that reason, a standard loading rate of 2-kips per min was established for the static tests.

3.1.3. Continuous Span 4 X 22 Slab Specimen

Test Procedure

The continuous 4 X 22 slabs were tested in the manner indicated by figures 5 and 8. Only partially

visible in figure 5 is an air-bag system underneath the

slab. Prior to the pull-out tests, the air pressure in the bag was adjusted to provide a uniform dis- tributed load of 90 psf. This load is equal to a roof

load of 30 psf plus 60 psf which is half the design load

for inserts spaced at 5 ft on centers.

It should be noted that not all the 19 inserts shown in figures 5 and 8 were pulled. Generally,

every other insert was pulled, until failure, and then

the balance were pulled out. However, many times,

the first pull-out damaged the specimen in such a

6
manner that the neighboring inserts might have been

affected. When this happened, the neighboring

inserts were not pulled.

Companion 4X4 specimens were tested at the same age as the 4 X 22 specimens using the regular

static test procedure.

3.1.4. Simple Span 4 X 22 Specimen Test Procedure

Three 4 X 22 specimens were tested with a simple

span of 20 ft in a manner similar to that used for the

continuous slabs. Due to the smaller load capacity no

simulated live load was applied by an air bag

system. Each of these slabs contained only five

inserts. The two inserts near the end were tested as

if they were in 4 X 4 specimens after the midspan

inserts had been pulled.

3.1.5. Waffle Slab Specimen Test Procedure

Four Type 3 inserts were embedded in the waffle

slab concrete at the four interior intersections of the

6-in ribs, as shown in figure 7. This test was to determine if the pull-out strength of inserts embedded in a waffle slab was affected by the relatively

thin section of concrete around the insert. It should

be noted that standard practice usually results in the placement of two reinforcement bars in both

directions at the bottom of the ribs. This practice,

which was followed for this test, results in the inserts being positioned so that the bars are close to the

insert on the four sides. The inserts were tested

using the 42-in test stand placed on the transverse

ribs. 3.2. Sustained Load Tests

3.2.1. Sustained Load Test Equipment

The sustained load equipment was designed to hold a constant tensile load on inserts embedded in

4X4 specimens. Figure 9 is a picture of some of the

specimens under sustained load. The sustained

loading equipment was the same as the static load

equipment, except that a 15-kip spring was used in

place of the hydraulic ram. The spring, which was

used to provide the required sustained load, was

Figure 9. Sustained load tests on 4 >< 4- specimen.

compressed by using a 60-kip ram. The load developed by the compres.sed spring was m(!asur(;d with

the load cell and adjusted periodically. Movfrment of the pull-out relative to the transverse; (idgcs of f;ach specimen was measured with 0.001-iti dial gauges, which are visible in figure 9.

3.2.2. Sustained Load Test Procedure

Four batches of concretes, designed as C-1, C-2,

C-3, and C-4, were used in preparing the 4X4

specimens used in the sustained load tests. C-1 and

C-3 specimens were normal weight concrete, and C-2

and C-4 were semi-lightweight concrcite. The purpose

of the tests was to determine the maximum load

which can be carried by an insert for an indefinitely

long period of time. Two types of sustained load tests were attempted. The first type of test consisted of slowly increasing the load at a constant rate, until

failure occurred.'' The rate of loading was varied

from 0.045 kips/h to 2.0 kip.s/min so as to get a

relationship between failure load and rate of loading.

The second, and the more conventional type of sustained load test, consisted of maintaining a predetermined pull-out load on the insert. The load was maintained using the springs visible in figure 9. The magnitude of the load to be sustained was

determined after ordinary short-term static pull-out

tests were performed on companion 4X4 specimens.

The sustained loads applied were 80, 85, and 90

percent of the short term pull-out loads. The move- ment of the pull-out rod relative to the edge of the

specimen, which included some deflection of the

slab, was measured at intervals of time, so that

creep movement vs time could be plotted.

3.3. Fatigue Loading Tests

3.3.1. General

Two series of fatigue tests were made on inserts embedded in 4§-in thick slabs. The first series of

tests were on inserts embedded in 4X4 slabs,

while the second series were on inserts embedded in 4 X 16 slabs. One of the most important variables in fatigue

tests is the ratio of the cyclic portion of the test load. This variable is usually expressed as the ratio (R)

of the minimum to the maximum load. JNIurdock and

Kesler [6] have shown that, for plain concrete in

flexure, the fatigue strength (10 million cycles) is about 55 percent of the static short-term strength,

when R = 0.0. When R = 0.3, the fatigue strength

is about 65 percent, and when R = 0.6, the fatigue

strength is about 80 percent. In this study R was

varied from 0.3 to 0.43.

3.3.2. Fatigue Loading Test Equipment

Figure 10 is a general view of the fatigue tests on

two 4 X 16 specimens. Alternating tensile loads of the required magnitude were applied by 10-kip

servo-controlled hydraulic rams, reacting against a

steel frame bolted to the laboratory tie-down floor.

* This loading scheme is a modification of the "Prot Method" (5] sometimes used in cycUc fatigue testing.

7
FLOW CHART

Figure 10. Fatigue tests on 16 specimen.

The test specimens were held to the tie-down floor at their reaction points. Both 4 X 16 and 4X4

specimens were tested under fatigue loading. The

4X16 specimen pictured in figure 10 was tested with

a span of 10 ft. The test span for the fatigue tests on

the 4X4 specimen was 42 in. Two fatigue tests were made on each 4 X 16 specimen, but only one on each 4X4 specimen.

3.3.3. Fatigue Tests on 4X4 Specimens

Twleve 4X4 fatigue test specimens were cast from each of the F-1, F-2, F-3, and F-4 concretes. Type 1 inserts were cast in the F-1, F-2, and F-3

specimens. Four inserts of each of the three types were cast in the F-4 slabs. The strength of the F-1

specimens was so great that the fatigue tests could not be made with the available equipment. The

4X4 specimens were fatigue loaded oh a span of 42 in, with a minimum load (Pmin) of 3.0 kips for all specimens. The maximum load (Pmax) was varied so that Pmin/-Pmax {R) varlcd from 0.30 to about 0.43.

3.3.4. Fatigue Tests on 4 X 16 Specimens

Longer fatigue test specimens were cast from the

X2-A, X2-B, X2-C, and X2-D concretes. Four

specimens containing Type 3 inserts were cast from

each concrete. The inserts were spaced so that each

specimen had two inserts available for fatigue

tests on a 10 ft span. Thus a total of eight fatigue

tests were made on specimens from each concrete. These fatigue specimens also contained inserts at

either end for determination of the static strength in a 4X4 specimen (figure 10). The maximum and

minimum load values were varied, but their ratio

{R) was held constant at 0.63 for these tests. It should be remembered that this ratio is less severe than that used for the 4X4 slabs of section 3.3.3.

4. Discussion of Results

4.1. General

The variables studied in this project are summarized here and in the flow chart of figure 11. Six

» First Priority Parameter Interactio

- Second Priority Monitoring

PRELIMINARY INVESTIGATION

01 INSERT TYPES

VARIABILITY DUE TO

INSERT TYPE

VARIABILITY OUETO

AGGREGATE TYPE

NORMAL AGGREGATE

FATIGUE LOAD

EFFECT

FLEXURAL

TENSION EFFECT

ANGULAR

LOAD

BEHAVIOR

RE-BAR

SPACING EFFECTS

CONCRETE

COVER

EFFECT

STATISTICAL ANALYSIS OF TESTSENGINEERING

ANALYSIS

OF TESTS

DESIGN RECOMMENDATIONS

Figure 11. Project flow chart.

insert types were tested in a preliminary investigation [4]. Three of these were eliminated from this study because they did not meet a Post Office

specification requiring malleable iron inserts suitable

for attaching |-in-diameter threaded rods. The three acceptable inserts were tested in 4 X 4

panels to determine if insert type or aggregate type was more critical. These tests are described in section

4.2. Based on these tests it was decided that aggre- gate type was more significant than insert type for the three inserts investigated. Subsequent tests were carried out with aggregate type as the major

variable.

4.2. Effect of Aggregate and Insert Type

Table 5 fists the results of tests performed on 4X4 specimens during the early stages of the in- vestigation. In order to minimize project complexity,

these initial results were used to decide whether to emphasize aggregate-type or insert-type as the more

significant parameter.

Since concrete L-4 was the only fully lightweight concrete (lightweight fines and lightweight coarse),

it was deleted from the statistical observations used

to compare normal weight concrete and semilightweight concrete (lightweight coarse only).

Note that the results of tests on Type L-4 were

significantly lower than the tests on semi-lightweight

concrete of comparable strength. This suggests that

8
Table 5. Tests for aggregate and insert variation

Average pull-out load* Concrete

Test set no. compressive

strength Type 1 Type 2 Type 3

fc'

psi kips kips kips H-1 3480 12.0 10.0 12.0 H-2 3150 15.8 12.5 14.6 H-1A 3950 16.2 14.9 17.4 H-2A 4110 14.5 13.5 13.1

L-1 2640 11.6 10.2 11.5

L-2 3040 9.9 8.0 8.9

L-3 5420 11.5 10.9 10.3 L-4 3300 9.3 7.2 7.3

T ^ OO/fJ 11.5 9.2 10.6 L-IA 5050 15.8 15.3 14.1 L-2A 5200 13.4 11.8 11.5

* Average of 4 Insert Pull-Out Tests.

data for semi-lightweight concrete should not be

directly extrapolated to fully lightweight concrete without additional testing. Table 6 summarizes some

elementary statistics computed to show the relationship between the insert type and the concrete type.

Referring to these statistics, it was decided that a two-part partitioning of the test distribution into

normal and semi-lightweight concrete would be the

most meaningful (as indicated in figure 11, section

4.1). Insert Type 3 was selected as the reference

insert to which the other two inserts could be compared.

Typical specimen failures are illustrated in

figures 4 and 12. In general, the base of the pull-out cone was about the same area for the Type 1 as for the Type 3 insert, but smaller in area for the Type 2. Type 1 and 3 inserts did not appear to be damaged

by the tests. However, in about 70 percent of the

tests, the wire loop of the Type 2 insert failed near

Table 6. Elementary statistics for concrete and insert type

Pull-out load

Concrete No.

Insert type type Sample Range samples mean

kips kips

1 Normal 14.6 7.3 16 2 Normal 12.7 6.8 16 3 Normal 14.3 8.3 16

1 Semi-light 12.3 7.9 24

2 Semi-light 10.9 7.6 24

3 Semi-light 11.2 6.8 24

All Normal 14.0 8.3 48

All Semi-light 11.5 9.3 72

1 All 13.2 8.1 40

2. .-r All 11.6 8.9 40

3 All 12.4 9.9 40

the point where it was welded to the spool. Even

when the loop did not fracture, the loop wires were

visibly necked down.

4.3. Concrete Strength-Weif^hl Effects

Over 200 static tests on 4X4 spccirnr-as were

a,bout equally divided into normal weight and semilightweight concrete specimens. Within each concrete type the variables were concrete; strength and

insert type. The failure mode shown in figure 12 is primarily a concrete tensile failure. 8inc(; concrete

tensile strength is approximately proportional to the square root of the concrete compressive strength,

the pull-out loads were examined as a linear function

of the square root of the concrete compressive

strength for the normal weight and semi-lightweight

specimeas.

Figure 12. Typical pull-out cone failure.

The data for normal weiglit concrete specimens

are shown in figure 13 along with two straight lines. The solid line is a linear least-squares fit [7, S] to the' data. The dashed line is proportional to the least- squares line and is intended to account for experimental scatter and other variables not accounted for by the least-squares equation. The least squares

equation for the normal weight concrete is given by:'

P^k = 1.Q3 + O.lSVfc' 4.3(1)

where Pn, is the insert pull-out strength in normal

weight 4X4 specimens (kips)

.

It is evident in figure 13 that the least-squares line

is not an ideal fit to the data. However, it is the

simplest prediction equation for these data since

there is no failure hypothesis available that considers all of the parameters affecting insert pull-out

strength.

Scatter'* was investigated by assuming that the

pull-out load is a linear function only of the square

root of the concrete compressive strength. Thus the

effect of variable concrete strength can be reduced

by using this relationship to normalize all pull-out

loads to a reference concrete strength. Figure 14

shows the distribution of all normal weight concrete 4X4 tests. The solid line histogram is for actual

pull-out loads. The dashed line histogram is for

5 Scatter as used here includes all variations other than those due to concrete tensile strength.
20.0

15.0

I 0,0

5.0

0.0

45.

P.. =1.63+0.18 Vf'c

P

50. 5 5 . 60. 65. 70. 75. 80.

SQUARE ROOT OF CONCRETE COMPRESSIVE STRENGTH h/f^),^/ Psi Figure 13. Variation of pull-out load with the square root of concrete strength for normal weight concrete.

40 -

30 -

o

d 20

10 -

4X4 SPECIMENS NORMAL WEIGHT CONCRETE

r--NORMALIZEO f ^= 3000 psi

ACTUAL f' (VARIES)

I

I ,

_] I I 1 I J Zl I 1- 8 10 12 14 16 18

PULL-OUT LOAD, Kip

Figure 14. Histogram of normal weight concrete pull-out loads m 4 X 4 specimens.

20

normalized pull-out loads based on a reference concrete compressive strength of 3000 psi. The

normalized load, P„, is equal to the actual pull-out

load, P, times the ratio of the square root of the

reference concrete strength to the square root of the

actual concrete strength

Pn = PVfc' = 3000 psi/Vactual //.

Referring to the normalized histogram, the average

pull-out load is 11.5 kips with a standard deviation

of 1.2. Using these data and assuming a normal

distribution of pull-out loads, a pull-out load can

be determined which most (say 95 percent) of the

test results exceed. Thus it was determined that

95 percent of the pull-out loads exceed 9.4 kips

which is 82 percent of the average pull-out load. The dashed line shown in figure 13 is the least- squares equation Une multiplied by 82 percent. Note

that most of the data are above this line. Thus the

reduced least-squares line is a conservative approxi10
mation of the pull-out load and at the same time it makes allowance for increased pull-out load with

increased concrete strength.

The semi-lightweight concrete data were handled

in a similar manner. The data are shown in figure 15

along with the least-square fit and the reduced line to account for scatter. The least-squares line shown

in figure 15 is given by:

3.06 + 0.13V/c' 4.3(2)

where is the insert pull-out strength in semilightweight 4X4 concrete specimens.

Th(^ histograms for actual and normalizt'd [julUjut

loads arc shown in figure 1(5. Referring to the

normalized histogram, the average; pull-out load is 10.2 kips with a standard deviation of 1.5. Using

these data it was determimd that 95 p(;rcerit of the

test results exc(H;d 7.7 kips which is 75 percent of the

a,verage pull-out load. This indicates that the semilightweight specimens exhibit slightly more scatter

20.0 1—

I 5.0

10.0

5.0

0.0

P4^ = 3.06+O.I3^/f^

X I 45. 50. 55, 60 . 6 5 . 70. 7 5.

SQUARE ROOT OF CONCRETE COMPRESSIVE STRENGTH (VfT'.'^^Psi'

8 0.

Figure 15. Variation of pull-out load with the square root of concrete strength for

semi-lightweight concrete.

40

30

20

10

4X4 SPECIMENS

SEMI-LIGHTWEIGHT CONCRETE

NORMALIZED f^, = 3000 psi

I 8 10 12 14 PULL-OUT LOAD, Kip

16 20

Figure 16. Histogram of semi-lighlweight concrete pull-out loads in 4X4 specimens.

11
Table 7. Comparison of empirical and test results—4 X 4 specimens

Pull-out load (Piu) by concrete type

Nominal

strength

of Normal- Semi-light- Lightweight weight weight

(Wc = 142 (Wc = 118 {W, = 96

lb /f t^) lb /f t^) lb /ft')

psi kip kip kip

T^Itti ni n fa 1 * 3000 1

1

Q Q a . 8Q Q O . O 3000 11.5 10.2 8.1

oOOO 14.1 12.0 10.2

Test** 5000 14.3 12.3

* Empirical P,u = 2.0 -|- .0012 WcVfc' (kips). ** Test results are the average of all samples within the range of the nominal concrete strength.

than the normal weight specimens. Note that most

of the data he above the reduced least-squares line. In comparing figures 13 and 15 the relative effects of concrete unit weight may be introduced. The

average unit weight of the normal weight concretes (Wh) was 142 Ib/ft^ The average unit weight of the

semi-lightweight concretes (Ws) was 118 Ib/ft^

Thus the ratio of unit weights (Wh/W^) is 1.20. For 3,300 psi concrete, the calculated regression

equations give:

Pik = 1.63 + 0.18^3,300 = 12.0 kips, 4.3(3)

Pis = 3.06 + 0.13x73,300 = 10.6 kips. 4.3(4)

Since P^h/Pis = 1.13 is close to the unit weight

ratio of 1.20, there may be a linear proportionality

relationship between concrete unit weight and the

insert pull-out strength. To investigate this possibility, consider the twelve tests on concrete L-4

(Table 5). For this lightweight concrete, the unit

weight iWi) was 96 lb/ft^ and the concrete strength was 3300 psi. If the unit weight ratio is a good

approximation, then the average pull-out strength

of these tests should be 8.3 kips.

The experimental average of the twelve tests was

7.9 kips. Although the results of twelve tests were

insufficient to form a final conclusion for the lightweight, the available evidence points toward a

generalized insert pull-out strength equation of the

form:

P4„ = 2.0 + 0.00121;F,v7c' 4.3(5)

where

:

Piu = the insert pull-out strength in 4 X 4 specimen (kips),

Wc = the unit weight of concrete (Ib/ft^),

// = the compressive strength of concrete (psi)

.

Equation 4.3(5) was obtained by modifying the

second term of Eqs. 4.3(1) and 4.3(2) to include the

concrete unit weight. The constant 0.0012 was then

obtained by averaging the constants from the second

term of the two modified equations. The constant 2.0 was then selected somewhat arbitrarily so that the

general equation does not produce pull-out loads

larger than those obtained from equations 4.3 ( 1 ) or

4.3(2). Loads obtained from the general equation

range from two to four percent lower than those obtained from the equations 4.3(1) and 4.3(2).

Based on this empirical equation insert pull-out

loads were calculated for 3,000 and 5,000 psi concrete. Table 7 compares these empirical results with

experimental averages. As can be seen, the comparisons are well within acceptable limits. Since the i equation is empirical it is limited to the range of the

test data which is for concrete compressive strengths

between about 3,000 to 5,000 psi. Scatter factors should be applied to the equation depending on the \ type of concrete.

[

4.4. Effect of Flexural Cracking

The pull-out strength of an insert is largely dependent on the tensile capacity of the embedding

concrete. If this capacity is reduced by tensile cracking resulting from flexural action, then insert pull-out strength would decrease.

To study the effects of slab bending moment

(flexural cracking) on insert strength, four long slabs

(4 X 22 specimens) were constructed with inserts on 12-in centers. These slabs were supported at three

reaction points on 10-ft centers to simulate the condition of a 4|-in thick slab continuous over two spans. Simulation of a uniform live load of 90 psf on three

of the slabs (S-1, S-2, and S-3) was accomplished

using air bags. Figure 5 shows the test setup. One

additional continuous slab (specimen S-4) was

tested with uniform live load of 150 psf.

Figures 17, 18, and 19 show the results of the

insert pull-out tests performed on the three con- tinuous slabs with 90-psf load. Slab S-1, shown by

figure 17, contained Type 1 inserts. Slab S-2,

shown by figure 18, contained Type 2 inserts, and

Slab S-3 of figure 19 contained Type 3 inserts. Four

control tests were performed on 4 X 4 specimens for slabs S-1, S-2, and S-3. The average of the control

tests is represented on the respective figures by a horizontal line. Slab S-4, shown by figure 20, contained Type 1 inserts but was loaded with 150 psf

12
4

lO' 4— 10' 1

'

4

*

r f^

20

18

16

X-O

g 12

10

!

«

2 6

4

2

, SLAB S-l

I INSERT TYPE I CONTROL TESTS AVERAGE STRENGTH

J L J I_LJ L

10 12 14 I 6

DISTANCE, ft Figure 17. Variation of pull-out strength with insert location in slab S-l.

18 20

r lO' lO' l'

i .0'°^ ^ V*^-^*^^i'^f'^ •^'t*^^ -C^,^-'^ S'r

DISTANCE, ff Figure 18. Variation of pull-out strength with insert location in slab S-2.

of simulated live load. No 4X4 specimen data

are available for Slab S-4. Each of figures 17, 18, 19, and 20 shows a positional effect on insert pull-out strength. This effect was investigated further in figure 21 by plotting

normalized pull-out load versus insert distance from

the nearest support. The pull-out loads wore nor- malized to a common concrete strength of .'),000 psi for ease in comparing slab data (3,000 psi was the

average compressive strength for the four slabs).

The normalized load, P„, is equal to the actual

pull-out load, P, times the ratio of the square root of

13
Figure 19. Variation of pull-out strength with insert location in slab S-3.

1' 10

'

lO' l'

H lU —

10 12 DISTANCE, ft

Figure 20. Variation of pull-out strength with insert location in slab

the reference concrete strength to the square root of the actual concrete strength

Ph = PVfc' = 3000 psi/Vactual //.

This is a reasonable procedure since pull-out load

was shown to be a linear function of s/f/ in section

4.3. This procedure assumes all insert types are equal although there are slight differences as indi- cated in section 4.2. The large pull-out strengths for inserts close to

14
I I I I I I I I

I

I I I I

I

I SLAB INSERT f'^ , psi 3830

394 0

31 10 2640

-P = 1.63 + 0.18 V3000

4h

= 1 1.5 kips -AVERAGE P= 10.5 kips FOR INSERTS MORE THAN 2' FROM NEAREST SUPPORT

I'll

DISTANCE FROM NEAREST

jSUPPORT IN 4X4 SPECIMENS

I I I I I I I I I I I I I 2. 0 3.0 4.0

DISTANCE FROM NEAREST SUPPORT, ft

Figure 21. Effect of distance from support on pull-out strength of inserts embedded in reinforced concrete slabs.

the supports can be attributed largely to the containing influence of the support reactions. Since the

insert pull-out cone varied from 12 in to 20 in diameter it is unlikely that the reactions affected

inserts farther than about 2 ft from the supports.

The data in figure 21 for inserts farther than 2 ft from the nearest support had an average pull-out

load of 10.5 kips. This is shown in the figure by a

solid line. Although the scatter is large (about S to

14.5 kips) , there seems to be no definite variation in load with distances greater than 2 ft from the support. The average load of 10.5 kips compares to a computed load of 11.5 kips based on equation

4.3(1) for a 4 X 4 slab. This indicates that equation

4.3(1) may give results about 10 percent too large

for slabs with spans greater than 4 ft. Bending

moments cannot be computed exactly for slabs S-1

through S-4 due to some uncertainties in support

conditions. Approximate calculations and test observations indicate that the tension steel probably

did not yield.

Three 20 ft simply supported slabs (X-20A,

X-20B, and X-20C) were tested in order to investi- gate the effect of reinforcement yield on the pull-out

strength. Slab X-20A had an average pull-out

strength of 7.1 kips (f/ = 4090 psi), slab X-20B

had an average pull-out strength of 6.8 kips (f/ =

3,100 psi), and slab X-20C had an average pull-out

strength of 6.4 kips {f/ = 3,200 psi). The inserts slipped out of the concrete due to numerous large

flexural cracks (steel had yielded) rather than

pulling out a cone of concrete as shown in figure 12. These test results indicate that yielding of tension

reinforcement should not be allowed since it permits

the formation of large cracks which change the

failure mode and reduce the pull-out strength by

30 to 40 percent. This is not a serious problem since

usual design procedures prevent the main ten.siori steel from yielding.

4.5. Effect of Reinforcement Cover and

Spacing

4..'5.1. Concrclc Cover

Table 8 lists the results of tests performed to study

the effects of reinforcement spacing and v.oncrcAc cover. Test specimens were the 4X4 concrete slabs with Type 3 insert. Test No. XlB-1 through XlB-9

were performed as three sets of three tests, each set with a different amount of concrete cover (f in, 1| in, and 3 in) over the reinforcing steel. Reinforcement for each set consisted of No. 5 bars at 12 in on centers, to simulate a condition of maximum

reinforcement spacing. In addition, a fourth control

set (XlB-10 through XlB-12) was included with

No. 5 bars at 6 in on centers, to reference the maximum spacing condition with a more common

design situation. Within the test range (f-in to 3-in clear cover) , the

experimental results in figure 22 indicate a linear

strength loss of about 1.4 kips per in of increased

concrete cover over the reinforcing steel. As indicated in figure 12 the typical pull-out mode

of failure consists of an irregular cone of concrete

pulled out with the insert. If the reinforcing steel intercepts this failure cone some of the insert load

may be transferred to the reinforcing steel by

dowel action. With increasing cover the reinforcing

steel intercepts less of the failure cone. Hence

the above loss in strength is probably due partly to the vertical location of the reinforcing steel with

respect to the inserts. Some loss may also be due to the increased flexural cracking in the specimens with

decreased moment capacitj' which occurs with

increased cover.

4.5.2. Reinforcemcnl Spacing

Referring again to table 8, tests No. XlA-1

through XlA-9 were designed to study the effects of reinforcement spacing. The tests were performed as three sets of three tests, each set with a different

steel spacing (3| in, 6 in, 12 in). The concrete cover and percent reinforcement were held approximately

constant. From the test results shown in table 8,

it is observed that up to the 12 in spacing the steel location does not significantl.y affect insert strength

(average pull-out strengths of 14.7, 13.8, and 14.3 kips respectively).

4.5.3. Wafflle Slab Ribs

The single waffle slab (W-1) test was made to determine if the pull-out strength of an insert would be affected by the relatively thin section of concrete around the insert. The average pull-out

load for the four Type 3 inserts was 15.5 kips.

From the equation 4.3(2) the expected pull-out load

would be about 12 kips. These results indicate that

the pull-out strength of inserts embedded at the

intersection of 6-in ribs in similar waffle slabs

15
Table 8. Effect of reinforcement cover and spacing

Reinforcement

Pull-out Test no.

Size Spacingo.c. Cover

load Average Range

XlB-1 #5 - in 12

in

3 kips10.3

kips kips

XlB-2 #5...- 12 3. 9.9 10.1 0.4 XlB-3 #5 12 3 10.0 XlB-4 #5 12

4 u 9.0 XlB-5 #5 12 15 9.0 9.1 0.2 XlB-6 #5 12 15 9.2 XlB-7 #5 12 3 7.1 XlB-8 #5 12 3 6.8 7.0 0.4 XlB-9 #5 12 3 7.0 XlB-10 #5 6

3 10.4 XlB-11 #5 6

4

3 10.9 10.7 0.5 XlB-12 #5 6

4

3 10.9 XlA-1 #4 3i 3 13.8 XlA-2 #4 3i

4

3 14.3 14.7 2.2 XlA-3 #4 3§

4

3 16.0 XlA-4 #5 6

4

3 13.6 XlA-5 /?D

4

3 13.7 13.8 0.4 XlA-6 #5 6

4

3 14.0 XI A-7 2-#5 12

4

34 13.5 XlA-8 2-#5 12 3 13"9 14.3 1.9 XlA-9 2-#5 12

4

3I 15.4

Notes: 1. Concrete Type XIA was normal weight with/c' = 4560 psi.

2. Concrete Type XIB was normal weight with/c' = 2990 psi.

3. Insert Type 3 was used in all slabs.

CONCRETE COVER OVER REINFORCING, in

Figure 22. The effect of concrete cover on pull-out load.

16
Figure 23. Waffle slab after testing.

would be as good or better than that for those

embedded in the 4X4 specimens. Figure 23 is a photograph of the waffle slab after testing. The

crack pattern, accentuated by felt pen markings, is easily visible in this figure and shows how the

cracks tended to extend along the line just below

the reinforcement. There is no doubt that the inserts were restrained by the reinforcement, as evidenced

by the crack patterns in the ribs.

4.6. Sustained Load Behavior

Forty-eight 4X4 specimens were tested to study

the effect of sustained load on insert pull-out

strength. Twelve normal weight concrete specimens were cast from each of batches C-1 and C-3. Another

twelve semi-lightweight concrete specimens were

cast from each of batches C-2 and C-4.

Specimen groups C-1 and C-2 were tested by the

modified Prot method described in section 3.2.2. Although inconclusive, the data indicated that the

sustained pull-out strength would reach a minimum

Figure 24. Sustained load failure on 4 X 4 specimen. ,

of about 90 percent of the short term strength, at a

load rate of about 0.1 kip/h. At slower loading rates the data indicate that the sustained strength may

become greater than 90 percent. This unexpected

result requires further study for verification. Specimen groups C-3 and C-4 were tested by the more conventional procedure also described in section 3.2. For each type of concrete, the twelve

tests were subdivided into four groups of three

tests each. The first group was tested to determine

the static load capacity. Each of the remaining

three groups was tested at different sustained load

levels. These load levels were 80, 85, and 90 percent

of the insert pull-strength obtained by performing

the static load capacity tests on the companion

4X4 specimens. A typical sustained load failure

is shown in figure 24. The results of the sustained load tests are plotted on figure 25, as Deformation vs Time curves. Each

of the six curves represents the average of the three

NORMAL WEIGHT (P^) SEMI-LIGHTWEIGHT (P^) Ps AND Ph REPRESENT CONTROL

TEST STRENGTHS

30 40 50 60

TIME UNDER LOADS, DAYS

Figure 25. Insert movement variation with time in sustained load tests.

17
tests performed at the indicated load level. The

dashed curves represent semi-lightweight concrete,

while the solid lines apply to normal weight concrete. As shown on the figure, the only failure occurred for semi-lightweight concrete loaded to 90 percent of the equivalent static strength. For all other load

levels, the deformations are relatively small, stable,

and tending toward an asymptotic relationship with

respect to some upperbound deformation. These

other specimens were observed for a period of one

year without any indication of failure.

4.7. Fatigue Load Behavior

4.7.1. General

Approximately 50 fatigue tests were performed to study the effects of fatigue loading on insert pull-out

strength. Of these tests, 25 were performed on Type 3

inserts embedded in the 4 X 16 specimens and

tested with a beam span of 10 ft. The remaining 25

tests were performed on the three types of inserts embedded in 4 X 4 specimens. Each type of fatigue

test slab had 4X4 static control test specimens so that fatigue loads could be expressed as a ratio of the

static strength (Pmax/P4).

4.7.2. Normal Weight Concrete

Figure 26 is a semi-log plot of Pmax/-P4 vs number

of cycles causing fatigue failure. These tests were performed on Type 3 inserts embedded in 4 X 16

slabs made from two batches of normal weight

concrete. The ratio of the cyclic load {R =

-PminZ-Pmax) was held coustaut at 0.63. The averages

of the 4X4 static control tests for the two batches were 11.6 kips and 13.7 kips, which are close to the

mean load of all static tests at similar concrete

strengths.

The fatigue test results shown in figure 26 indi- cate that the fatigue strength at 2 million cycles is about 65 percent of the static strength for the 4X4

control specimens. In short term static tests on

companion specimens with a 10 ft span the insert strength was 87 percent of the strength for the

4X4 control specimens. This strength loss is in close agreement with the effects of flexural cracking (a

strength loss of about 10 percent) described in section 4.4. This indicates that about one-third of the

apparent strength loss in these fatigue tests was due

to the increased span and two thirds was due to

fatigue. In general the fatigue test slabs were reinforced by

No. 5 bars at 6 in on centers. To check the effect of reinforcement spacing on fatigue strength, one test slab from each batch was reinforced with No. 5

bars at 12 in on centers. As indicated on figure 26,

the reduction in steel did not significantly reduce the

insert fatigue strength.

4.7.3. Semi-Lightweight Concrete

The results of fatigue tests with 4 X 16 semilightweight concrete specimens are plotted in

figure 27. These tests were similar to those of figure

26, except that the test specimens were made from

two batches of semi-lightweight concrete. Type 3

inserts were embedded in the slabs. The average pull-out strength of the 4X4 static control tests was 10.8 kips, which is close to the mean

load of all 4 X 4 semi-lightweight tests. The fatigue

test results shown in figure 27 indicate that for 2

million cycles, the fatigue strength of an insert is

0 50

SPAN = 10 -0

f^-- 0.63 ma X

• t. -REINFORCING AT 12 c/c

J I I I I I 1 1 1

I I I I I I I II \ L_L

10,000 100,000

FATIGUE CYCLES (LOGARITHMIC)

1 , 000, 000

Figure 26. Effect of fatigue on pull-out loads in 10 ft spans of normal weight concrete specimens.

18
I .00

SPAN = 10 - 0

I I I I I I I II J I I 1 I I III _[_L

10,000 100,000

FATIGUE CYCLES (LOGARITHMIC)

1,000,000

Figure 27. Effect of fatigue on 'pull-out loads in 10 ft spans of semi-lightweight concrete specimens.

about 70 percent of the static strength for the 4X4

control specimens.

In static tests on compansion specimens with a

10 ft span the insert strength was 89 percent of the

strength for the 4X4 control specimens. This

strength loss is in close agreement with the effects of

flexural cracking (a strength loss of about 10 percent)

described in section 4.4 although those tests were on

normal weight concrete. Again this indicates that

about one third of the strength loss in these fatigue

tests was due to the increased span and two thirds was due to fatigue.

4.7.4. Variation of Insert Type and Ratio, R

Figure 28 shows the results of 25 fatigue tests performed on inserts embedded in 4 X 4 specimens.

These tests were used to mvestigate the effect of variation of insert type and variation of the ratio, R, on fatigue strength. However, there are insufficient data shown in figure 28 to permit reaching any

positive conclusions.

4.7.5. Fatigue Failures in Connecting Hardware

An important adjunct to the fatigue testing on

the inserts was the discovery that the fatigue limit

1,00

O.BO

0.60

I I I J_LLL

INSERT

1 2 3 NORMAL WEIGHT A •

SEMI-LIGHTWEIGHT A

0 30 < R - _mm_ <0.43

p

J I I I I I U I , 100,000„

I 1

1

10,000

FATIGUE CYCLES (LOGARITHMIC)

Figure 28. Effect of fatigue on pull-out loads in 4 X 4 specimens.

19
for some of the connecting hardware used in the

tests was close to that of the actual specimens being

tested. No record was kept of the individual bolts and clevis pins so that the full history of each is not known. However, the mortality rate for this hard- ware was around 50 percent of that for the insert specimens. This is not surprising when fatigue data,

such as has been presented in [9], is considered.

These data indicate that the fatigue strength of ordinary steel bolts can be as low as 20,000 psi for 10 million cycles. This means that for a safety factor

of 2.0, the allowable load under cyclic loading conditions on a I inch threaded steel bolt could be as low

as 3.0 kips.

4.8. Angular Load Effect

Referring to table 9, Tests No. X4A-1 through

X4A-12 were designed to investigate the effects of

Table 9. Effect of Angular Pull on Insert PuU-Out Load*

Test no. Load Insert Pull-out load

angle** angle**

Individual Average

X4A-1

degrees 0

degrees 0kips 11.8kips

-2 0 0 12 0 11.8

-3 0 0 11 7

-4 0 0 11 7

-5 20 0 12 4

-6 20 0 12 2 12.4

-7 20 0 12 6

-8 20 0 12 4

-9 0 20 13 1 -10 0 20 13 7 13.4

-11 0 20 13 2

-12 20 20 13 8 13.8

* Concrete Strength, // = 3440 psi. ** Measured from a plane perpendicular to the plane of the

slab.

intentional or unintentional misalinement of an in- sert or its connecting hardware. Tests X4A-1 through

X4A-4 were performed on well-alined inserts and

loads, for reference purposes. Tests X4A-5 through

X4A-8 were performed to determine if an angled load

decreased the insert pull-out strength. The results show no reduction in strength for a load 20 degrees out of alinement with a plane perpendicular to the

plane of the slab. Tests X4A-9 through X4A-11 were performed to

establish if an angled insert decreased the pull-out

strength. The results show no reduction in strength.

Slab X4A-12 was tested with the insert and load

both angled (but in line with each other). Again,

there was no reduction in strength.

5. Summary and Conclusions

5.1. General

This investigation was limited to cast-in-place

inserts with 3|- to 3f-in embedment lengths in 4|-in thick reinforced concrete slabs. Reinforcement

steel was No. 5 bars at 6 in on centers with |-in

clear cover unless stated otherwise.

5.2. Aggregate and Insert Type

All three types of inserts can be considered similar

for purposes of design load recommendations that

encompass flexure, fatigue, and sustained load

effects. Although the inserts behave similarly they

are not equivalent. Types 1 and 3 were generally

very close in performance, but with Type 2 testing

about one to two kips lower for similar loading

conditions. Nevertheless the inserts have been

considered equal with differences being accounted

for in section 5.9 on experimental scatter. The pull-out strength of the inserts was lower in specimens made with semi-lightweight concretes than in specimens made with the normal weight

concretes. This difference was slightly less for fatigue loading than it was for static loading.

5.3. Concrete Strength

From section 4.3, it is concluded that an increase in concrete compressive strength causes a predictable

increase in the average pull-out strength. For a

concrete strength between 3,000 and 5,000 psi,

and a concrete unit weight of 115 to 145 Ib/ft^, the

average static pull-out strength of the inserts in a

reinforced concrete slab 4X4 specimen can be

approximated by:

P4„ = 2.0 + 0.0012 W.Vfc' 5.3(1)

where

:

Piu = 4X4 specimen puUout strength (kips)

,

Wc = unit weight of concrete (Ib/ft^),

fc = concrete compressive strength (psi).

5.4. Concrete Flexural Cracking

Tests on slabs continuous over two 10-ft spans

indicate that insert pull-out strengths based on

simply supported 4X4 specimens may be 10

percent too high when the inserts are used in longer

spans where more flexural cracking occurs. Tests on

20-ft simply supported slabs indicate that yielding of

flexural reinforcement changes the insert mode of

failure. That is, the inserts slip out of the concrete due to large flexural cracks rather than puUing out a cone of concrete which is the typical mode of failure. This is not a serious problem since usual design

procedures prevent the main tension steel from

yielding. Insert pull-out loads obtained from 4X4

specimens should be multiplied by a reduction factor

<t>t = 0.90 to account for the loss of insert strength

due to flexural cracking.

20
5.5. Reinforcement Quantity and Cover

From the discussion of section 4.5.1, it is concluded

that for concrete covers greater than f in the insert capacity in a 4 X 4 specimen made with a 3,000 psi

normal weight concrete would be reduced by 1.4 kips per in of cover for up to 3 in of cover. These

tests did not include cover less than f in or greater

than 3 in. The reinforcement spacing study of section 4.5.2 shows that the loss of insert strength with No. 5

bars spaced up to 12 in, is relatively small and may

be neglected.

5.6. Sustained Load

It was shown in section 4.6 and figure 25 that a

sustained insert load 90 percent of the static pull-out

load can result in a failure in semi-lightweight

concrete slabs. Thus, if sustained load is to be

considered as a prime parameter, a reasonable

reduction factor (^J is 0.85. Since it is physically

impossible to develop maximum sustained load and

maximum fatigue load simultaneously, the maximum

effects of sustained load and fatigue load are not

cumulative. Since sustained load is not as detrimental

to the insert behavior as is fatigue load, it may be

unnecessary to consider this parameter, provided

fatigue loading has been considered.

5.7. Fatigue Load

For inserts subjected to cyclic loads, such as those

applied by vibrating mechanical equipment, a

fatigue load reduction factor should be considered.

Based on the results discussed in section 4.7, the

semi-lightweight concrete should have a fatigue

reduction factor (</>/s) of 0.70 and normal weight

concrete should have a 0.65 fatigue reduction factor

(<^>/ft). The fatigue tests were performed on 10-ft long concrete slabs, which means that these factors have incorporated in them a reduction due to

flexural tension cracking. It is also important to recognize that the probability of getting a fatigue

load and a sustained load large enough to adversely

affect the insert strength in a cumulative fashion is extremely small.

5.8. Angular Load Effect

No load reduction was observed with inserts and/or loads out of alinement up to 20 degrees as measured from a plane perpendicular to the plane of the slab.

5.9. Experimental Scatter Factor

Based on the discussion in section 4.3 for normal

weight and semi-lightweight concrete pull-out loads

normalized to 3,000 psi, it was concluded that

reduction factors are required to account for experimental scatter. In order to assume that 95 percent

of the pull-out loads are as large as the average

value in a 4 X 4 specimen an experimental scatter

factor for normal weight concrete (</>ca) of 0.82

should be used. A similar experimental scatter

factor for semi-lightweight concrete (</»es) is 0.75.

6. Design Criteria

6.1. Design RecommendationH

6.1.1. Dcsif^n Safely Margin

In sections 5.4 through 5.9 four reduction factors were defined. These arc summarized as follows: Experimental Scatter Factors,

Fatigue Reduction Factors,

Flexural Cracking Factor,

Sustained Load Factor,

<l>eh

<t>e» 4>/h

<t>/>

4>t

0.82

0.75

0.65

0.70

0.90

0.85

It is assumed that the individual reduction factors may be combined by cumulative multiplication to account for the effect of several variables in oru; factor. The combined fatigue reduction factor, 0^/, should include the effect of experimental scatter and fatigue. Since the fatigue tests were performed on

long slabs, the fatigue factors, ^/a and <^/, include a

flexural cracking effect. Sustained load does not need to be considered since this would not ordinarily occur with a fatigue load. Thus the combined fatigue

reduction factor for normal weight concrete, <i>cjh, is:

<i>cfh = <t>eh X <t>/h = 0.53 The similar factor, </»,/s, for semi-lightweight concrete

is:

<j>c/s = <t>es X <t>/s = 0.53

Since these factors are equal, only one combined

fatigue reduction factor, <^,/ = 0.53, needs to be

considered in design. This is the most severe combination of reduction factors. It is desirable to select a design safety margin to account for strength variations and occasional

structural overloads normally expected. In the

case of live loads, one commonly used load factor is 1/1.8 = 0.56 (See ACI 318-63). Combining this factor with the most conservative of the reduction

factors makes the total reduction factor (<^) 0.29.

6.1.2. Design Equations

The recommended design equation given below is limited to inserts of the type tested when embedded

in 4|-in thick concrete with |-in cover over rein- forcing steel. The equation is limited to concrete ranging in compressive strengths from 3,000 to 5,000 psi. Additional limitations are listed in section

6.2. Subject to the above restrictions, the recom- mended equation for the design load on an insert is: P = <A(2.0 + 0.0012IFcv7c')- G.l(l)

For <t> = 0.29, this becomes:

P = 0.58 + 0.00035 W^V/c' 6.2(2)

where

:

P = allowable design load per insert (kips)

,

Wc = unit weight of concrete (Ib/ft^),

fc = compressive strength of concrete (psi)

.

21
Some typical values of P have been tabulated in

table 10 for several different concrete strengths.

Table 10. Allowable design loads

Design loads

Normal- Semi-light- Concrete strength, f^' weight weight

concrete concrete

psi kips kips 3000 3.3 2.8 4000 3.7 3.2 5000 4.1 3.5

Notes:

1. Design loads computed for inserts embedded in concrete with unit weights of 142 lb /ft' for the normal weight and

118 lb/ft' for the semi-lightweight concrete.

2. Semi-lightweight concrete with lightweight coarse aggregates and fine aggregate of normpl-weight sand.

3. These are allowable design loads for only the inserts when embedded in 4^ in thick reinforced slabs made

with f in cover over reinforcing steel and made with the

specified concrete. The effect of the fatigue loading on

the connecting hardware must also be considered. In

general the maximum allowable load on an insert may

be fully controlled by the allowable load on the connecting hardware when cyclic loading is expected.

6.2. Precautions and Limitations

6.2.1. Connecting Hardware

The recommendations presented in this paper are

for inserts, similar to those tested, embedded in

properly placed reinforced concrete slabs. However,

the critical factor in the insert suspension system

subjected to fatigue loading may not be the pull-out

strength of the insert but the properties of the connecting hardware, specifically, the threaded rods.

It was pointed out in section 4.7.5 that approximately 50 percent of the hardware used in the

fatigue tests failed before the inserts. No specific

recommendations concerning connecting hardware

can be made since no records were kept of the indi- vidual bolts used in the fatigue tests. But it is apparent that allowable design insert loads as computed from the equation of section 6.1.2 and as presented in table 10 should be used only for moderate fatigue or static loading conditions unless the

fatigue properties of the connecting hardware are

fully considered.

6.2.2, Insert Spacing

If it is desirable to have inserts spaced closer than 3 ft on centers the allowable load on each

insert should be reduced. In light of the absence of data on this factor it seems advisable to limit insert loading so that the total design load on the inserts within any 3 ft diameter area is not greater than the

allowable load on a single insert. This needs research

because there could be situations where it would be

advantageous to group a number of inserts close together.

6.2.3. Inserts Other Than Those Tested

It is recommended that inserts, different from

those tested, be evaluated using the 4X4 reinforced

slabs and the static test procedures described

heretofore.

6,2.4. Inserts in Lightweight Aggregate Concretes When designing slabs to be made from either

lightweight or semi-lightweight concretes the allowable insert load may be less than the 3.0 kips,

normally used by many designers. If this 3.0 kips

insert load is considered to be the lower limit, the

design compressive strength for the lightweight

aggregate concrete may have to be increased. This

iacrease presents no problem for most of the aggregates produced at the present time. An alternate to

this increase in the concrete strength would be to require an increase in the unit weight of the concrete.

6.2.5. Installation of Inserts During this investigation a number of inserts were

"lost" while placing the concrete. This can easily

happen in the construction of an actual structure

since the method of holding the insert is not accidentproof. The concrete handlers should be warned to keep their tools and vibrator spuds away from the

inserts. In the laboratory good results were obtained

by assigning one man to be fully responsible for the

inserts and for placing the concrete around the

inserts.

If the loss of inserts is a major problem in the

field it may be necessary to design a better method

of holding the inserts while placing the concrete. In

the event of a missing insert some type of a drilled-in anchoring device would have to be estabhshed. The

design recommendations for inserts in this paper

do not apply to these other types of anchors.

The work described herein was carried out in the

structural laboratories of the 'Building Research

Division at the National Bureau of Standards. The

program was sponsored by the U.S. Post Office Department. Liaison with the Post Office Department was provided by W. J. Werner who is now with

the U.S. Department of Housing and Urban Development. Fraiik Erskine of the Expanded Clay and

Slate Institute, Washington, D.C., arranged for the

Institute's donation of the expanded shale lightweight aggregates.

Appreciation is extended to J. E. Breen, Professor

of Civil Engineering at the University of Texas at Austin, who reviewed the paper and made many

helpful suggestions.

22
7. References

[1] Hsu, T. T. C, and Hanson, N. H., An Investigation of Rail-to-Concrete Fasteners, Journal of the PCA Research and Development Laboratories 10, 3, 14—35 (Sept. 1968).

[2] Adams, Robert F., Some Factors Which Influence the Strength of Bolt Anchors in Concrete, ACI Journal 27,

2, 131-138 (Oct. 1955).

[3] Kennedy, Thomas B., and Crawley, Walter O., Tests of Anchors for Mass-Concrete Forms, ACI Journal 27, 2, 139-147 (Oct. 1955).

[4] Pull-Out Strength of Inserts Embedded in Reinforced Concrete Slabs, Unpublished Report to Sponsors (Nov.

1968).

fo] Prot, E., Fatigue Testing Under Progressive Ix)iMJing, Translation, USAF, WADC, Tl{ 52-148 (Sept. H)52j.

[6] Murdock, John W., Kesley, Clyde 10., JOfTect of iiaiige of Stress on Fatigue Strength of Plain C<HicrctX! BeurrLs, ACI Journal 30, 2, 221-231 (Aug. 1958).

[7] Natrella, M. C, Experimental Statistics, Nat. Bur. Stand.

(U.S.) Handb. 91 (Aug. 1963).

[8] Mood, A. M., and (iraybill, F. A., Introduction to the Theory of Statistics (McGraw-Hill Book Co., Inc., New

York, 1963).

[9] Schwartz, Andrew, Jr., New Thread Form Reduces Bolt Breakage, Steel 127 (Sept. 1950).

23
FORM NBS-114A (1-71) U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS BSS-422, Gov't Accession No.3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Design Loads for Inserts Embedded in Concrete

5. Publication Date April 1972

6. Performing Organization Code

7. AUTHOR(S)

To Wo Reichard, E, Fo Carpenter, Eo V, i,eyendecker

8. Performing Organization

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. 4213417

11. Contract/Grant No.

12. Sponsoring Organization Name and Address

U. S. Postal Service

Washington, D. C. 20005

13. Type of Report & Period Covered

Final

14, sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) Detailed test procedures are presented for a research program on cast-in-place

inserts embedded in reinforced concrete. Three types of insertSj two of malleable

iron and one of ductile steel, capable of receiving a 3/4 inch threaded rod were

testedo Other variables included concrete aggregate type, concrete strength,

reinforcement cover and spacing, angular loading, flexural cracking, sustained

load and fatigue loadingo

It was found that the pull-out load for an insert could be approximated by a linear

function of the concrete unit weight and square root of the compressive strength in

a statically loaded reinforced concrete slab. The effect of other variables is re- lated to the insert pull-out loads in these slabs. Design recommendations are presented .

17. KEY WORDS (Alphabetical order, separated by semicolons)

Anchors; concrete slabs; design loads; fatigue; inserts; pull-out loads; sustained

load .

18. AVAILABILITY STATEMENT 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

fXl UNLIMITED.

UNCLASSIFIED „

26

1 1 FOR OFFICIAL DISTRIBUTION. DO NOT RELEASE

TO NTIS.

20. SECURITY CLASS

(THIS PAGE)

22. Price $ .35

UNCLASSIFIED

J USCOMM-DC 66244-P7I
Announcement of New Publications in

Building Science Series

Superintendent of Documents,

U.S. Government Printing Office,

Washington, D.C. 20402

Dear Sir:

Please add my name to the announcement list of new publications to be

issued in the series : National Bureau of Standards Building Science Series.

Name

Company

Address

City State Zip Code .

( Notification key N-339

)
I
NBS TECHNICAL PUBLICATIONS

PERIODICALS JOURNAL OF RESEARCH reports National

Bureau of Standards research and development in physics, mathematics, chemistry, and engineering.

Comprehensive scientific papers give complete details of the work, including laboratory data, experimental

procedures, and theoretical and mathematical analyses. Illustrated with photographs, drawings, and

charts.

Published in three sections, available separately:

• Physics and Chemistry

Papers of interest primarily to scientists working in these fields. This section covers a broad range of physical and chemical research, with major emphasis on standards of physical measurement, fundamental

constants, and properties of matter. Issued six times a year. Annual subscription: Domestic, $9.50; $2.25

additional for foreign mailing.

• Mathematical Sciences

Studies and compilations designed mainly for the mathematician and theoretical physicist. Topics in mathematical statistics, theory of experiment design,

numerical analysis, theoretical physics and chemisty, logical design and programming of computers

and computer systems. Short numerical tables. Issued

quarterly. Annual subscription: Domestic, $5.00;

$1.25 additional for foreign mailing.

• Engineering and Instrumentation

Reporting results of interest chiefly to the engineer

and the applied scientist. This section includes many

of the new developments in instrumentation resulting

from the Bureau's work in physical measurement,

data processing, and development of test methods.

It will also cover some of the work in acoustics,

applied mechanics, building research, and cryogenic

engineering. Issued quarterly. Annual subscription:

Domestic, $5.00; $1.25 additional for foreign mailing.

TECHNICAL NEWS BULLETIN

The best single source of information concerning the Bureau's research, developmental, cooperative, and

publication activities, this monthly publication is designed for the industry-oriented individual whose

daily work involves intimate contact with science and

technology

for engineers, chernists, physicists, re- search managers, product-development managers, and

company executives. Annual subscription: Domestic,

$3.00; $1.00 additional for foreign mailing.

Order NBS publications from:

NONPERIODICALS

Applied Mathematics Series. Mathematical tables, manuals, and studies.

Building Science Series. Research results, test methods, and performance criteria of building materials, components, systems, and structures.

Handbooks. Recommended codes of engineering

and industrial practice (including safety codes) de- veloped in cooperation with interested industries,

professional organizations, and regulatory bodies.

Special Publications. Proceedings of NBS conferences, bibliographies, annual reports, wall charts,

pamphlets, etc.

Monographs. Major contributions to the technical

literature on various subjects related to the Bureau's

scientific and technical activities.

National Standard Reference Data Series.

NSRDS provides quantitative data on the physical

and chemical properties of materials, compiled from

the world's literature and critically evaluated.

Product Standards. Provide requirements for sizes, types, quality, and methods for testing various industrial products. These standards are developed co- operatively with interested Government and industry

groups and provide the basis for common understanding of product characteristics for both buyers and

sellers. Their use is voluntary.

Technical Notes. This series consists of communications and reports (covering both other agency and

NBS-sponsored work) of limited or transitory interest.

Federal Information Processing Standards

Publications. This series is the official publication

within the Federal Government for information on

standards adopted and promulgated under the Public

Law 89-306, and Bureau of the Budget Circular A-86

entitled. Standardization of Data Elements and Codes

in Data Systems.

Consumer Information Series. Practical information, based on NBS research and experience, covering

areas of interest to the consumer. Easily understandable language and illustrations provide useful background knowledge for shopping in today's technological marketplace.

NBS Special Publication 305, Supplement 1, Publications of the NBS, 1968-1969. When ordering, include Catalog No. C13. 10:305. Price $4.50;

$1.25 additional for foreign mailing.

Superintendent of Documents

Government Printing Office

Washington, D.C. 20402
U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington, D.C. 20234

OFFICIAL BUSINESS POSTAGE AND FEES PAID

U.S. DEPAHTMENT OF COMMERCE

Penalty for Private Use, $300